Marijuana risks for teens - as a parent, you may wonder about the true dangers associated with adolescent marijuana use - how harmful is it, really?

On the one hand, you don’t want to see your children taking
any drugs - but on the other hand, if they’re going to experiment with drugs
(and about half of all students will by the end of high-school*) maybe we should feel
grateful that it’s only marijuana, after all:

You may have used it (or use it) and experienced few
negative consequences.

It seems increasingly accepted and commonplace within
popular culture.

But here's the thing - though many adults can use marijuana without significant
adverse effects (though some will develop addiction) teens, with their still-developing brains, may experience lasting (lifelong!) adverse
consequences.

Marijuana is not as toxic as meth (or alcohol for that
matter) or as addictive as cigarettes, but it is still a powerful mind-altering
substance. Research shows that using it regularly during important developmental
stages causes lasting brain changes and functional impairments that can last a
lifetime.

However– if you can keep your child from developing a
marijuana habit until young-adulthood – say until the age of 21 – you help him/her
bypass virtually all of the risks associated with early marijuana use. You don’t
have to keep them from marijuana forever – just help them delay
initiation to when it won’t do so much harm.

In this article you will find out how marijuana affects the
still-developing teen brain and why a younger age of regular use increases the risks of
whole-life problems. This article will present research findings from major
studies which illustrate the increased risks associated with earlier marijuana
use across a range of domains, such as:

The cognitive consequences

The mental health consequences

The academic consequences

Addiction Issues

*According to the Monitoring the Future Survey Study, as of
2012, 49.1% of high school seniors had tried at least some kind of illicit
drug at least once and 45.2% of grade 12 students had tried marijuana at least
once.1

The Cognitive Consequences of Marijuana Use

The research summaries below demonstrate that adolescent
marijuana users experience thinking and impulse control deficits
that may diminish academic performance and increase the likelihood of
bad-decision making.

Regular users will experience these deficits at all times
(not only while high) but these deficits are reversible with sustained
abstinence – so after a month or so of avoiding marijuana, thinking powers
return to normal.

However, regular users who start smoking at a young age do
not demonstrate this same recovery with abstinence. If you get heavily into
marijuana in young adolescence, you can cause lasting brain damage that may
limit your whole-life potential - even after you stop using.

The Effects on Current Thinking
Abilities

If your son or daughter smokes a lot of marijuana as a teen,
will they be as sharp during their high school years?

Possibly not. This is likely dose-dependent (the more you
smoke, the greater the impact) but research shows that adolescents who smoke
marijuana do not perform as well on tests of short term memory and impulse
control as teens who do not use marijuana. These deficits could easily affect
school performance.2 Other studies have shown that teen marijuana users may also show deficits in
verbal and non-verbal short term memory, processing speed, attention and
executive functions.3

Marijuana's Effects on
Lifetime Thinking Abilities

If you smoke marijuana as a teen, will it affect your
potential as an adult?

Unfortunately, research suggests that adolescent marijuana
use can have a lasting influence, especially with a young age of initiation.

The University of Oregon Study

Adolescents who smoke heavily (defined as 4 days a week or
more) may do irreversible brain damage and shave-off a significant chunk of
potential I.Q.4

University of Oregon Researchers examined data from a pool
of over a thousand people who were followed from birth in 1973/74 to age 38.
All subjects were assessed for I.Q. at age 13 and each subject was interviewed
about marijuana use patterns at ages 18, 21, 26, 32 and 38.

The Results:

At age 38:

Subjects who started smoking as adolescents were more likely
to become heavy persistent smokers into adulthood than those who started in
young adulthood.

Heavy marijuana smokers scored worse on measures of I.Q.,
memory and concentration than those who abstained from marijuana.

Subjects who began smoking as adults but then cut back as
they aged recovered from the cognitive deficits associated with marijuana use,
but those who smoked heavily in young adolescence did not show the
same cognitive recovery, even after cutting back with age.

Subjects who smoked heavily as teens lost an average of 8
I.Q. points over the ages of 13 to 38. This is considered a significant
decline.

As an associational study the authors cannot prove that
marijuana use causes irreversible I.Q. deficits, nevertheless, the study
authors postulate that marijuana may be toxic to the adolescent brain in a way
that it is not to the adult brain.

The Harvard Study

Researchers at Harvard tested the cognitive performance of
three groups of adult study subjects. Subjects in the first group were
non-users. Subjects in group 2 were heavy using adults who had started using
marijuana after the age of 17 (late onset) and subjects in group 3 were heavy
using adults who had started using prior to age 17 (early onset). All marijuana
users had been abstinent for at least 28 days at the time of cognitive testing.

After 28 days of abstinence, adults who had started smoking
marijuana after the age of 17 showed no differences in cognitive performance to
non-using adults. Subjects from the early onset group, however, performed
significantly worse in cognitive tests, particularly tests of verbal
intelligence, even after 28 days of abstinence.5

Brazilian Study

Cognitive testing on treatment-seeking chronic adult
marijuana users shows that those who started with marijuana prior to the age of
15 perform significantly worse on measures of executive functioning (working
memory, problem solving, cognitive flexibility and planning) than those who
started after the age of 15.6

Attention Dysfunction Study

The brain’s visual scanning system matures greatly during a
developmental stage that occurs between 12 and 15 years of age.

When testing adult study subjects on a quick-reaction
computer task that involved visual scanning ability, subjects who had initated
regular marijuana use prior to age 16 (early onset) performed significantly
worse than subjects who initiated use after age 16 (late onset). Late onset marijuana users performed
equally well to control subjects, indicating that marijuana is toxic to the
visual system during certain developmental stages.7

Observable Brain Changes

Beyond observing differences in thinking,
researchers can also see how an early age of marijuana onset causes MRI visible brain
alterations. Earlier ages of onset
are associated with progressively decreased white matter integrity8 and decreased cortical thickness.9

Academic Consequences of Teen Marijuana Use

While there are always exceptions, in general, students who
use marijuana get lower grades than students who abstain. The Washington State
Healthy Youth Survey Study revealed that marijuana using high school students
were more likely to get Cs, Ds and Fs than non-users.10

Given that current marijuana use impairs attention, working
memory and impulse control it’s hardly surprising to find an association
between use and lower school performance – but are there unique academic risks
associated with earlier age of regular use?

Yes, as with cognitive consequences, earlier age of regular
use is associated with greater declines in school performance.

Australian researchers found that teens who started smoking
marijuana at least once a week by the age of 15 were far more likely to drop
out of school prior to completion than students who started with weekly use at
an older age or those who abstained from marijuana - the younger the age of
regular use – the greater the risk of school drop-out prior to completion.11

Postulated explanations for why marijuana use - especially
early onset use – is associated with academic underachievement include:

Marijuana-caused learning difficulties

Greater involvement with non-academically oriented peers

Or, it could be that young people attracted to early
marijuana use are also more exposed to other risk factors that also predict
school non-completion.12

Mental Health Consequences

Adolescents who smoke marijuana raise their risk of
developing a psychotic disorder in adulthood and smoking earlier in adolescence
increases the dangers.13

A major Swedish study
found that smoking heavily by the age of 18 raises your risk of adult
schizophrenia by 600%.

A follow-up study from New Zealand replicated
the increased risk findings. In this study, the researchers found that people who
had smoked marijuana by the age of 15 were 4 times more likely than control
subjects to be diagnosed with schizophrenia by the age of 26 and that those who
started at 15 were at greater risk to develop schizophrenia than subjects who
started after the age of 18.14

Who’s Most at Risk?

Not every teenager using marijuana has the same schizophrenia
risk. Teens more at risk include:15

Those with a close family member with psychosis or another
serious mental illness.

Those who have already had an unusual psychological experience
after using marijuana (such as a break from reality).

Addiction Consequences

The younger a person starts using marijuana, the greater the
risks of lifetime addiction.

The earlier in adolescence a person starts using, the more
rapidly addiction develops.16

Take-Home Message

Whatever your opinion on marijuana for adults, it seems
clear that initiating regular use before the age of 18 puts an adolescent at
risk of serious and lasting neurocognitive deficits. In fact, given that the
brain continues to mature and develop to the age of 25, it seems likely that
delaying marijuana use even beyond the age of 18 would be prudent – to that end, the California Society of Addiction Medicine advocates helping young
adults delay first use to the age of 21.17

If Concerned about a Teen Not Currently Using

Talk to your children about marijuana. Don’t scaremonger
(you’ll lose credibility if you do) and don’t stray from the facts, but make
sure you explain that marijuana is dangerous to teens in a way that
it is not to adults - and that starting young could have lasting or even
irreversible consequences.

If Concerned about a Teen already Using

Communicate the facts, and consider interventions
(counseling, etc.) if necessary, to help this person achieve behavioral
change.

Helpful Reading:

Thinking about giving up marijuana but not sure you’re ready to take the plunge? Well, here are 70 benefits of quitting – all first-hand accounts from previously heavy users about how life changes for the better once you don’t need to get high all the time.